1. Field of the Invention
The present invention relates to an optical disk including a plurality of information recording layers, wherein at least two information recording layers are provided with recording learning regions for determining optimal recording parameters respectively, to a method for manufacturing such a disk, as well as to a method for recording and a method for reproducing data using such an optical disk.
2. Related Background Art
In recent years, as the recording density and the capacity of optical disks increase, it is becoming more important to ensure the reliability of optical disks. Accordingly, to ensure reliability, a technology has been proposed in which the optical disk is provided with a recording learning region, and a recording learning process is performed to determine the recording parameters by carrying out a test recording on this recording learning region (see for example JP 2001-338422A). “Recording learning” means the operation of optimizing the pulse parameters related to the laser light that is irradiated onto the optical disk during the recording. The pulse parameters include, for example, the power of the laser pulses irradiated onto the optical disk during recording, as well as the timing at which the laser pulses are generated, and their length.
Furthermore, there is vigorous research in optical disks whose recording capacity is doubled by arranging an information recording layer that is semi-transparent for recording and reproducing laser light on the side from which laser light is irradiated (i.e. frontward), and arranging a further information recording layer behind that, thus providing a dual-layer structure. Also in such dual-layer optical disks, recording learning is necessary, and a technology has been proposed, in which both the frontward information recording layer (referred to as “L1 layer”) and the rearward information recording layer (referred to as “L0 layer”) are subjected to the learning of recording parameters prior to the recording of data (see for example JP 2000-311346A).
However, there is the possibility that the optimal recording parameters for the L0 layer cannot be extracted through this recording learning operation. In recording learning, it is conceivable that test signals are recorded at a power that is considerably higher than the recording power that is optimal for the recording of data (optimum recording power). Thus, even in optical disks in which the presence of recordings in the L1 layer does not affect the quality of recordings to the L0 layer at the optimum recording power, there may be intensity changes when the laser light passes through the L1 layer at a test recording power that is relatively high, and it is conceivable that the optimum recording power for the L0 layer cannot be obtained by a recording learning operation.